Fully integrated dc SQUID magnetometers for ultra low frequency noise applications have been designed, fabricated and characterized. The basic design of the sensor is based on the Ketchen-type magnetometer. A moat surrounding the washer have been inserted to reduce 1/f noise due to hopping of flux vortices, trapped in the SQUID body during the cool-down process. To decrease flux motions in the pick-up coil structure a turn width as small as possible has been used. Further Josephson junctions with a high areas have been employed to reduce the 1/f arising from critical currant fluctuations. An additional positive feedback (APF) circuit and a feedback coil for Flux-Locked-Loop (FLL) have been integrated on the same chip to avoid any additional noise due to an external APF circuit. Details about design criteria and experimental results concerning voltage-flux characteristics and noise performances of the devices are presented. Due to a low magnetic field noise, such devices well meet the requirements of ultra-low frequency noise applications.
Fully integrated dc SQUID magnetometers for ultra low frequency noise applications
CGranata;
2003
Abstract
Fully integrated dc SQUID magnetometers for ultra low frequency noise applications have been designed, fabricated and characterized. The basic design of the sensor is based on the Ketchen-type magnetometer. A moat surrounding the washer have been inserted to reduce 1/f noise due to hopping of flux vortices, trapped in the SQUID body during the cool-down process. To decrease flux motions in the pick-up coil structure a turn width as small as possible has been used. Further Josephson junctions with a high areas have been employed to reduce the 1/f arising from critical currant fluctuations. An additional positive feedback (APF) circuit and a feedback coil for Flux-Locked-Loop (FLL) have been integrated on the same chip to avoid any additional noise due to an external APF circuit. Details about design criteria and experimental results concerning voltage-flux characteristics and noise performances of the devices are presented. Due to a low magnetic field noise, such devices well meet the requirements of ultra-low frequency noise applications.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
